const promise = new Promise(function (resolve) {
	setTimeout(() => {
		var a = 'hello '
		resolve(a);
	}, 10);
})

promise.then((a) => {
	return new Promise(function (resolve) {
		setTimeout(() => {
			var b = a+'lagou '
			resolve(b);
		}, 10);
	})
})
.then((b) => {
	setTimeout(() => {
		var c = 'i love you'
		console.log(b+c);
	}, 10);
})